Long-wave irradiance from the atmosphere may be measured in renewable energy applications, meterological and climatological studies to determine the amount of infrared radiation, both direct and indirect, reaching the Earth's surface, changes in long term climate, etc. To measure the long-wave irradiance, a pyrgeometer is typically used. Pyrgeometers are devices that measure the atmospheric infra-red radiation spectrum that extends approximately from 4.5 micrometers to 100 micrometers. In general, pyrgeometers comprise a thermopile sensor that converts thermal energy caused by absorbed radiation into electrical energy. Typically, the thermopile is located under a filtered silicon dome or window that acts as a short-wave filter such that only the long-wave radiance reaches the thermopile. Thus, by measuring the voltage generated by the thermopile, the long-wave radiance of the atmosphere may be determined.
To accurately measure the long-wave irradiance of the atmosphere, pyrgeometers are typically calibrated to an international standard. In general, manufacturers of pyrgeometers calibrate the pyrgeometers by obtaining a pyrgeometer that has been compared to and calibrated to an internationally recognized reference. Thus, each manufactured pyrgeometer has traceability back to a world standard. However, to date, the international pyrgeometer standard is based on a calculation obtained from an artificial atmosphere created in a blackbody device. In general, the blackbody device utilizes a viscous material to create long-wave irradiance within an enclosed dome under specific constraints that is then measured by a thermopile device. Through this measurement, several coefficients of the blackbody device may then be computed and, subsequently, used to calibrate additional pyrgeometers. In this manner, pyrgeometers from around the world may be calibrated to an international standard based on the blackbody device to normalize the measurements obtained from the pyrgeometers.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.